Answer:
See explanation.
Step-by-step explanation:
D. 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d8;
Explanation: before filling 3d orbitals, 4s needs to be filled. Since s holds 2 electrons, take two from the 3d10.
E. 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p3;
Explanation: after the 4s orbital, the 3d orbitals need to be filled. You do not fill the 4d orbitals until the 5s orbital is filled.
Here is a quick review of the order orbitals need to be filled in:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p;
s holds 2 electrons; p holds 6 electrons; d holds 10 electrons; f holds 14 electrons.